Polypeptides and polynucleotides of the present invention are believed to be important immunogens for specific prophylactic or therapeutic immunization against tumors, because they are specifically expressed or highly over-expressed in tumors compared to normal cells and can thus be targeted by antigen-specific immune mechanisms leading to the destruction of the tumor cell. They can also be used to diagnose the occurrence of tumor cells. Furthermore, their inappropriate expression in certain circumstances can cause an induction of autoimmune, inappropriate immune responses, which could be corrected through appropriate vaccination using the same polypeptides or polynucleotides. In this respect the most important biological activities to our purpose are the antigenic and immunogenic activities of the polypeptide of the present invention. A polypeptide of the present invention may also exhibit at least one other biological activity of a CASB7439 polypeptide, which could qualify it as a target for therapeutic or prophylactic intervention different from that linked to the immune response.